Added support for stdin input

.vscode/launch.json

@@ -0,0 +1,17 @@
+{
+  // Utilisez IntelliSense pour en savoir plus sur les attributs possibles.
+  // Pointez pour afficher la description des attributs existants.
+  // Pour plus d'informations, visitez : https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Launch Package",
+      "type": "go",
+      "request": "launch",
+      "mode": "auto",
+      "program": "${fileDirname}",
+      "env": {},
+      "args": ["-c", "test.txt"]
+}
+  ]
+}

main.go

@@ -11,18 +11,43 @@ import (
 	"unicode/utf8"
 )
 
-func byteCounter(f *os.File) {
+func isInputFromPipe() bool {
+	fileInfo, _ := os.Stdin.Stat()
+	return fileInfo.Mode()&os.ModeCharDevice == 0
+}
+
+func fileByteCounter(f *os.File) int64 {
 	fileInfo, err := f.Stat()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
-	fmt.Println(fileInfo.Size())
+	return fileInfo.Size()
 }
 
-func lineCounter(f io.Reader) {
+func stdinByteCounter(f *os.File) int64 {
 	buf := make([]byte, 32*1024)
-	count := 0
+	count := int64(0)
+
+	for {
+		c, err := f.Read(buf) // c==0 if EOF
+
+		switch {
+		case err == io.EOF:
+			return count
+
+		case err != nil:
+			fmt.Fprintf(os.Stderr, "error: %v\n", err)
+			os.Exit(1)
+		}
+
+		count += int64(c)
+	}
+}
+
+func lineCounter(f io.Reader) int64 {
+	buf := make([]byte, 32*1024)
+	count := int64(0)
 	lineSep := []byte{'\n'}
 
 	for {
@@ -30,21 +55,20 @@ func lineCounter(f io.Reader) {
 
 		switch {
 		case err == io.EOF:
-			fmt.Println(count)
-			return
+			return count
 
 		case err != nil:
 			fmt.Fprintf(os.Stderr, "error: %v\n", err)
 			os.Exit(1)
 		}
 
-		count += bytes.Count(buf[:c], lineSep)
+		count += int64(bytes.Count(buf[:c], lineSep))
 	}
 }
 
-func wordCounter(f io.Reader) {
+func wordCounter(f io.Reader) int64 {
 	buf := make([]byte, 32*1024)
-	count := 0
+	count := int64(0)
 	wordSep := []byte{' ', '\t', '\n', '\r', '\f', '\v'}
 	inWord := false
 
@@ -56,8 +80,7 @@ func wordCounter(f io.Reader) {
 			if inWord {
 				count++
 			}
-			fmt.Println(count)
-			return
+			return count
 
 		case err != nil:
 			fmt.Fprintf(os.Stderr, "error: %v\n", err)
@@ -77,15 +100,15 @@ func wordCounter(f io.Reader) {
 	}
 }
 
-func charCounter(f *os.File) {
+func charCounter(f *os.File) int64 {
 	var line string
 	var err error
 	r := bufio.NewReader(f)
-	count := 0
+	count := int64(0)
 
 	for err == nil {
 		line, err = r.ReadString('\n')
-		count += utf8.RuneCountInString(line)
+		count += int64(utf8.RuneCountInString(line))
 	}
 
 	if err != io.EOF {
@@ -93,17 +116,32 @@ func charCounter(f *os.File) {
 		os.Exit(1)
 	}
 
-	fmt.Println(count)
+	return count
 }
 
 func main() {
+	var f *os.File
+	var fileName string
+	var byteCounter func(f *os.File) int64
 
 	cFlag := flag.Bool("c", false, "print the byte count")
 	lFlag := flag.Bool("l", false, "print the line count")
 	wFlag := flag.Bool("w", false, "print the word count")
 	mFlag := flag.Bool("m", false, "print the character count")
 	flag.Parse()
-	fileName := flag.Arg(0)
+
+	if isInputFromPipe() {
+		f = os.Stdin
+
+		if flag.NFlag() != 1 {
+			fmt.Fprintf(os.Stderr, "must provide a single flag to gowc when reading from stdin\n")
+			flag.Usage()
+			os.Exit(1)
+		}
+
+		byteCounter = stdinByteCounter
+	} else {
+		fileName = flag.Arg(0)
 
 		if len(fileName) == 0 {
 			fmt.Fprintf(os.Stderr, "gowc [flags] filename\n")
@@ -111,21 +149,38 @@ func main() {
 			os.Exit(1)
 		}
 
-	f, err := os.Open(fileName)
+		var err error
+		f, err = os.Open(fileName)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "error: %v\n", err)
 			os.Exit(1)
 		}
 		defer f.Close()
 
+		byteCounter = fileByteCounter
+	}
+
 	switch {
 	case *cFlag:
-		byteCounter(f)
+		fmt.Print("\t", byteCounter(f))
 	case *lFlag:
-		lineCounter(f)
+		fmt.Print("\t", lineCounter(f))
 	case *wFlag:
-		wordCounter(f)
+		fmt.Print("\t", wordCounter(f))
 	case *mFlag:
-		charCounter(f)
+		fmt.Print("\t", charCounter(f))
+	default:
+		b := byteCounter(f)
+		f.Seek(0, 0)
+		l := lineCounter(f)
+		f.Seek(0, 0)
+		w := wordCounter(f)
+		fmt.Print("\t", l, "\t", w, "\t", b)
+	}
+
+	if len(fileName) > 0 {
+		fmt.Println("\t", fileName)
+	} else {
+		fmt.Println("")
 	}
 }